This invention relates to a direct current motor having a wound armature provided with a plurality of insulated windings.
It is well known that a direct current (DC) motor provided with a plurality of armature windings formed by lap winding or by wave winding techniques is highly efficient and has better commutating characteristics as the number of armature windings increases. If the conventional manner of lap winding or wave winding is employed in a coreless motor, however, the armature of motor will increase in thickness because the armature windings are superposed on each other in many layers. The increased thickness of the armature will substantially reduce the effective magnetic field of the field magnet passing through the armature, resulting in decreased motor efficiency and decreased motor starting torque. The prior art effort for solving these problems, has been directed to reducing the thickness of the conductor portions, which contribute to generate torque, by specially processing the edge portions of the coils. This processing for reducing the thickness of conductor portions was performed by a working such as press molding and, accordingly, was often accompanied by such as the breaking and short-circuiting of the armature windings. Further, since phase relationship between the armature windings could not be positively held in a desired state at the time the windings were arranged, correct phase relationship between the windings was distorted. Accordingly, it was very difficult to obtain a DC motor having an efficiency which is as high as theoretically expected. In addition, such prior art DC motors could not be mass produced and were costly. In another prior art technique used for conventional cylindrical coreless DC motors, superposition of the edge portions of coils of armature windings on each other was avoided by winding insulated wire in alignment turn by turn so that the entire width of winding, or a part thereof, was slanted with respect to the rotating axis. This technique, however, was also costly and could not be employed for mass production.